1. Field of the Invention
This invention relates to a novel, aluminum atom- and monocarboxylic acid residue-containing polyester, adhesives comprising such polyester, and laminates and laminated hollow vessels comprising such polyester as a constituent element.
2. Description of the Prior Art
Polyesters, typically polyethylene terephthalate, are enjoying an increasing demand in the manufacture not only of fibers and of films but also of containers for food and drink and of food packaging films owing to their favorable mechanical properties, transparency, heat resistance, electrical characteristics, and the like. Since such polyester containers and films, to a certain extent, function as gas barriers, their use is favorable for the preservation of food and drink and the like. However, for certain kinds of food and drink which are to be packed therewith or contained therein, further improvement in gas barrier function is demanded.
Attempts heretofore have been made to provide laminated containers and films using a polyester and another resin superior thereto in gas barrier function (especially, an ethylene-vinyl alcohol copolymer). Thus, for instance, Japanese Kokai Tokkyo Koho No. 56-77,144 and Japanese Kakai Tokkyo Koho No. 57-128,516 disclose laminated hollow vessels made of a polyester and an ethylene-vinyl alcohol copolymer. These hollow vessels, however, show a marked tendency to interlayer separation because the adhesion between the polyester and the ethylene-vinyl alcohol copolymer is poor and no adhesive is used for uniting both the polymer layers with each other.
Japanese Kokai Tokkyo Koho No. 53-108,162 discloses a laminated hollow vessel comprising a polyester layer and an ethylene-vinyl alcohol copolymer layer adhered together with an adhesive blend of the materials of both the layers, namely the polyester and the ethylene-vinyl alcohol copolymer, and Japanese Kokai Tokkyo Koho No. 56-117,653 discloses a laminated hollow vessel made of a polyester and an ordinary ethylene-vinyl alcohol copolymer adhered together by means of a high ethylene content ethylene-vinyl alcohol copolymer. However, such adhesives are still insufficient to provide good interlayer adhesion and accordingly the hollow vessels produced by using them are not suited for practical use. In particular, the low adhesion strength between the adhesive layer and the polyester layer has been a problem.
Accordingly, development of an adhesive capable of firmly adhering a polyester layer to an ethylene-vinyl alcohol copolymer layer or of an improved polyester for use as a base capable of adhering to a carboxyl-containing polyolefin adhesive which is known to adhere well to an ethylene-vinyl alcohol copolymer has been strongly demanded so that laminated articles can be produced from a polyester and an ethylene-vinyl alcohol copolymer.